Fix seams on generated item models (MC-73186) (#437)

This PR fixes the large seams on generated item models, fixing
[MC-73186](https://bugs.mojang.com/browse/MC-73186) for these models.
Non-generated models and models which entirely replicate the item model
generation should be unaffected.

patches/net/minecraft/client/renderer/block/model/ItemModelGenerator.java.patch

@@ -1,6 +1,16 @@
 --- a/net/minecraft/client/renderer/block/model/ItemModelGenerator.java
 +++ b/net/minecraft/client/renderer/block/model/ItemModelGenerator.java
-@@ -39,6 +_,8 @@
+@@ -32,13 +_,16 @@
+
+             Material material = p_111672_.getMaterial(s);
+             map.put(s, Either.left(material));
+-            SpriteContents spritecontents = p_111671_.apply(material).contents();
+-            list.addAll(this.processFrames(i, s, spritecontents));
++            TextureAtlasSprite sprite = p_111671_.apply(material);
++            // Neo: fix MC-73186 on generated item models
++            list.addAll(net.neoforged.neoforge.client.ClientHooks.fixItemModelSeams(this.processFrames(i, s, sprite.contents()), sprite));
+         }
+
          map.put("particle", p_111672_.hasTexture("particle") ? Either.left(p_111672_.getMaterial("particle")) : map.get("layer0"));
          BlockModel blockmodel = new BlockModel(null, list, map, false, p_111672_.getGuiLight(), p_111672_.getTransforms(), p_111672_.getOverrides());
          blockmodel.name = p_111672_.name;

src/main/java/net/neoforged/neoforge/client/ClientHooks.java

@@ -74,10 +74,12 @@
 import net.minecraft.client.renderer.ShaderInstance;
 import net.minecraft.client.renderer.block.BlockRenderDispatcher;
 import net.minecraft.client.renderer.block.model.BakedQuad;
+import net.minecraft.client.renderer.block.model.BlockElement;
 import net.minecraft.client.renderer.blockentity.BlockEntityRenderDispatcher;
 import net.minecraft.client.renderer.blockentity.BlockEntityRenderer;
 import net.minecraft.client.renderer.culling.Frustum;
 import net.minecraft.client.renderer.texture.TextureAtlas;
+import net.minecraft.client.renderer.texture.TextureAtlasSprite;
 import net.minecraft.client.renderer.texture.atlas.SpriteSourceType;
 import net.minecraft.client.resources.language.I18n;
 import net.minecraft.client.resources.model.BakedModel;
@@ -1063,6 +1065,44 @@ public static <T extends BlockEntity> boolean isBlockEntityRendererVisible(Block
         return renderer != null && frustum.isVisible(renderer.getRenderBoundingBox((T) blockEntity));
     }
 
+    /**
+     * Modify the position and UVs of the edge quads of generated item models to account for sprite expansion of the
+     * front and back quad. Fixes <a href="https://bugs.mojang.com/browse/MC-73186">MC-73186</a> on generated item models.
+     * 
+     * @param elements The generated elements, may include the front and back face
+     * @param sprite   The texture from which the elements were generated
+     * @return the original elements list
+     */
+    public static List<BlockElement> fixItemModelSeams(List<BlockElement> elements, TextureAtlasSprite sprite) {
+        float expand = -sprite.uvShrinkRatio();
+        for (BlockElement element : elements) {
+            // Edge elements are guaranteed to have exactly one face, anything else is either invalid or the front/back
+            if (element.faces.size() != 1) continue;
+
+            var faceEntry = element.faces.entrySet().iterator().next();
+            if (faceEntry.getKey().getAxis() == Direction.Axis.Z) continue;
+
+            // Move edge quads to account for sprite expansion of the front and back quads
+            element.from.x = Mth.clamp(Mth.lerp(expand, element.from.x, 8F), 0F, 16F);
+            element.from.y = Mth.clamp(Mth.lerp(expand, element.from.y, 8F), 0F, 16F);
+            element.to.x = Mth.clamp(Mth.lerp(expand, element.to.x, 8F), 0F, 16F);
+            element.to.y = Mth.clamp(Mth.lerp(expand, element.to.y, 8F), 0F, 16F);
+
+            float[] uv = faceEntry.getValue().uv.uvs;
+            // Counteract sprite expansion on edge quads to ensure alignment with pixels on the front and back quads
+            if (faceEntry.getKey().getAxis() == Direction.Axis.Y) {
+                float centerU = (uv[0] + uv[0] + uv[2] + uv[2]) / 4.0F;
+                uv[0] = Mth.clamp(Mth.lerp(expand, uv[0], centerU), 0F, 16F);
+                uv[2] = Mth.clamp(Mth.lerp(expand, uv[2], centerU), 0F, 16F);
+            } else {
+                float centerV = (uv[1] + uv[1] + uv[3] + uv[3]) / 4.0F;
+                uv[1] = Mth.clamp(Mth.lerp(expand, uv[1], centerV), 0F, 16F);
+                uv[3] = Mth.clamp(Mth.lerp(expand, uv[3], centerV), 0F, 16F);
+            }
+        }
+        return elements;
+    }
+
     // Make sure the below method is only ever called once (by forge).
     private static boolean initializedClientHooks = false;
 

src/main/java/net/neoforged/neoforge/client/model/DynamicFluidContainerModel.java

@@ -114,7 +114,7 @@ public BakedModel bake(IGeometryBakingContext context, ModelBaker baker, Functio
 
         if (baseLocation != null && baseSprite != null) {
             // Base texture
-            var unbaked = UnbakedGeometryHelper.createUnbakedItemElements(0, baseSprite.contents());
+            var unbaked = UnbakedGeometryHelper.createUnbakedItemElements(0, baseSprite);
             var quads = UnbakedGeometryHelper.bakeElements(unbaked, $ -> baseSprite, modelState, modelLocation);
             modelBuilder.addQuads(normalRenderTypes, quads);
         }
@@ -124,7 +124,7 @@ public BakedModel bake(IGeometryBakingContext context, ModelBaker baker, Functio
             if (templateSprite != null) {
                 // Fluid layer
                 var transformedState = new SimpleModelState(modelState.getRotation().compose(FLUID_TRANSFORM), modelState.isUvLocked());
-                var unbaked = UnbakedGeometryHelper.createUnbakedItemMaskElements(1, templateSprite.contents()); // Use template as mask
+                var unbaked = UnbakedGeometryHelper.createUnbakedItemMaskElements(1, templateSprite); // Use template as mask
                 var quads = UnbakedGeometryHelper.bakeElements(unbaked, $ -> fluidSprite, transformedState, modelLocation); // Bake with fluid texture
 
                 var emissive = applyFluidLuminosity && fluid.getFluidType().getLightLevel() > 0;
@@ -140,7 +140,7 @@ public BakedModel bake(IGeometryBakingContext context, ModelBaker baker, Functio
             if (sprite != null) {
                 // Cover/overlay
                 var transformedState = new SimpleModelState(modelState.getRotation().compose(COVER_TRANSFORM), modelState.isUvLocked());
-                var unbaked = UnbakedGeometryHelper.createUnbakedItemMaskElements(2, coverSprite.contents()); // Use cover as mask
+                var unbaked = UnbakedGeometryHelper.createUnbakedItemMaskElements(2, coverSprite); // Use cover as mask
                 var quads = UnbakedGeometryHelper.bakeElements(unbaked, $ -> sprite, transformedState, modelLocation); // Bake with selected texture
                 modelBuilder.addQuads(normalRenderTypes, quads);
             }

src/main/java/net/neoforged/neoforge/client/model/ItemLayerModel.java

@@ -70,7 +70,7 @@ public BakedModel bake(IGeometryBakingContext context, ModelBaker baker, Functio
         CompositeModel.Baked.Builder builder = CompositeModel.Baked.builder(context, particle, overrides, context.getTransforms());
         for (int i = 0; i < textures.size(); i++) {
             TextureAtlasSprite sprite = spriteGetter.apply(textures.get(i));
-            var unbaked = UnbakedGeometryHelper.createUnbakedItemElements(i, sprite.contents(), this.layerData.get(i));
+            var unbaked = UnbakedGeometryHelper.createUnbakedItemElements(i, sprite, this.layerData.get(i));
             var quads = UnbakedGeometryHelper.bakeElements(unbaked, $ -> sprite, modelState, modelLocation);
             var renderTypeName = renderTypeNames.get(i);
             var renderTypes = renderTypeName != null ? context.getRenderType(renderTypeName) : null;

src/main/java/net/neoforged/neoforge/client/model/geometry/UnbakedGeometryHelper.java

@@ -33,6 +33,7 @@
 import net.minecraft.client.resources.model.ModelState;
 import net.minecraft.core.Direction;
 import net.minecraft.resources.ResourceLocation;
+import net.neoforged.neoforge.client.ClientHooks;
 import net.neoforged.neoforge.client.model.ElementsModel;
 import net.neoforged.neoforge.client.model.ExtraFaceData;
 import net.neoforged.neoforge.client.model.IModelBuilder;
@@ -112,10 +113,10 @@ public static BakedModel bake(BlockModel blockModel, ModelBaker modelBaker, Bloc
     }
 
     /**
-     * @see #createUnbakedItemElements(int, SpriteContents, ExtraFaceData)
+     * @see #createUnbakedItemElements(int, TextureAtlasSprite, ExtraFaceData)
      */
-    public static List<BlockElement> createUnbakedItemElements(int layerIndex, SpriteContents spriteContents) {
-        return createUnbakedItemElements(layerIndex, spriteContents, null);
+    public static List<BlockElement> createUnbakedItemElements(int layerIndex, TextureAtlasSprite sprite) {
+        return createUnbakedItemElements(layerIndex, sprite, null);
     }
 
     /**
@@ -124,19 +125,20 @@ public static List<BlockElement> createUnbakedItemElements(int layerIndex, Sprit
      * <p>
      * The {@link Direction#NORTH} and {@link Direction#SOUTH} faces take up the whole surface.
      */
-    public static List<BlockElement> createUnbakedItemElements(int layerIndex, SpriteContents spriteContents, @Nullable ExtraFaceData faceData) {
-        var elements = ITEM_MODEL_GENERATOR.processFrames(layerIndex, "layer" + layerIndex, spriteContents);
+    public static List<BlockElement> createUnbakedItemElements(int layerIndex, TextureAtlasSprite sprite, @Nullable ExtraFaceData faceData) {
+        var elements = ITEM_MODEL_GENERATOR.processFrames(layerIndex, "layer" + layerIndex, sprite.contents());
+        ClientHooks.fixItemModelSeams(elements, sprite);
         if (faceData != null) {
             elements.forEach(element -> element.setFaceData(faceData));
         }
         return elements;
     }
 
     /**
-     * @see #createUnbakedItemMaskElements(int, SpriteContents, ExtraFaceData)
+     * @see #createUnbakedItemMaskElements(int, TextureAtlasSprite, ExtraFaceData)
      */
-    public static List<BlockElement> createUnbakedItemMaskElements(int layerIndex, SpriteContents spriteContents) {
-        return createUnbakedItemMaskElements(layerIndex, spriteContents, null);
+    public static List<BlockElement> createUnbakedItemMaskElements(int layerIndex, TextureAtlasSprite sprite) {
+        return createUnbakedItemMaskElements(layerIndex, sprite, null);
     }
 
     /**
@@ -145,10 +147,11 @@ public static List<BlockElement> createUnbakedItemMaskElements(int layerIndex, S
      * <p>
      * The {@link Direction#NORTH} and {@link Direction#SOUTH} faces take up only the pixels the texture uses.
      */
-    public static List<BlockElement> createUnbakedItemMaskElements(int layerIndex, SpriteContents spriteContents, @Nullable ExtraFaceData faceData) {
-        var elements = createUnbakedItemElements(layerIndex, spriteContents, faceData);
+    public static List<BlockElement> createUnbakedItemMaskElements(int layerIndex, TextureAtlasSprite sprite, @Nullable ExtraFaceData faceData) {
+        var elements = createUnbakedItemElements(layerIndex, sprite, faceData);
         elements.remove(0); // Remove north and south faces
 
+        SpriteContents spriteContents = sprite.contents();
         int width = spriteContents.width(), height = spriteContents.height();
         var bits = new BitSet(width * height);
 

tests/src/main/resources/assets/custom_fluid_container_test/models/item/custom_fluid_container.json

@@ -1,6 +1,11 @@
 {
-  "parent": "item/generated",
+  "parent": "neoforge:item/default",
+  "loader": "neoforge:fluid_container",
+  "fluid": "minecraft:empty",
+  "cover_is_mask": true,
   "textures": {
-    "layer0": "item/bucket"
+    "base": "item/bucket",
+    "fluid": "neoforge:item/mask/bucket_fluid_drip",
+    "cover": "neoforge:item/mask/bucket_fluid_cover_drip"
   }
 }